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Li Y, Shi H, Yin G. Synthetic techniques for thermodynamically disfavoured substituted six-membered rings. Nat Rev Chem 2024:10.1038/s41570-024-00612-3. [PMID: 38822206 DOI: 10.1038/s41570-024-00612-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/26/2024] [Indexed: 06/02/2024]
Abstract
Six-membered rings are ubiquitous structural motifs in bioactive compounds and multifunctional materials. Notably, their thermodynamically disfavoured isomers, like disubstituted cyclohexanes featuring one substituent in an equatorial position and the other in an axial position, often exhibit enhanced physical and biological activities in comparison with their opposite isomers. However, the synthesis of thermodynamically disfavoured isomers is, by its nature, challenging, with only a limited number of possible approaches. In this Review, we summarize and compare synthetic methodologies that produce substituted six-membered rings with thermodynamically disfavoured substitution patterns. We place particular emphasis on elucidating the crucial stereoinduction factors within each transformation. Our aim is to stimulate interest in the synthesis of these unique structures, while simultaneously providing synthetic chemists with a guide to approaching this synthetic challenge.
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Affiliation(s)
- Yangyang Li
- The Institute for Advanced Studies, Wuhan University, Wuhan, Hubei Province, China
| | - Hongjin Shi
- The Institute for Advanced Studies, Wuhan University, Wuhan, Hubei Province, China
| | - Guoyin Yin
- The Institute for Advanced Studies, Wuhan University, Wuhan, Hubei Province, China.
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2
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Irie Y, Yokoshima S. Total Synthesis of Putative Melognine. J Am Chem Soc 2024; 146:9526-9531. [PMID: 38546412 DOI: 10.1021/jacs.4c02086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Total synthesis of melognine was accomplished. A 10-membered cyclic alkyne was prepared via an intramolecular SN2 reaction of a nosylamide. Enyne metathesis of the cyclic alkyne under an atmosphere of ethylene afforded a 1,3-diene. Intramolecular cycloaddition of a nitrone and an azomethine ylide with the 1,3-diene moiety constructed the characteristic highly fused skeleton. Further transformation, including ring-closing metathesis, resulted in the synthesis of melognine, whose NMR spectra did not match the reported data. Close inspection of the spectra of melognine in the literature suggested that the structure of melognine might be identical with that of a known alkaloid, melodinine L.
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Affiliation(s)
- Yui Irie
- Graduate School of Pharmaceutical Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Satoshi Yokoshima
- Graduate School of Pharmaceutical Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
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3
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Sennari G, Yamagishi H, Sarpong R. Remote C-H Amination and Alkylation of Camphor at C8 through Hydrogen-Atom Abstraction. J Am Chem Soc 2024; 146:7850-7857. [PMID: 38447162 DOI: 10.1021/jacs.4c01351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2024]
Abstract
Camphor continues to serve as a versatile chiral building block for chemical synthesis. We have developed a novel method to functionalize the camphor skeleton at C8 using an intramolecular hydrogen atom abstraction. The key advance involves the use of a camphor-derived aminonitrile, which is converted to the corresponding nitrogen-centered radical under photoredox conditions to effect the 1,5-hydrogen atom transfer at C8. The resulting carbon-centered radical at C8 was utilized in a C-H amination to access topologically complex proline derivatives. Furthermore, the total synthesis of several sesquiterpenoids was accomplished by engaging the radical generated at C8 in alkylation reactions.
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Affiliation(s)
- Goh Sennari
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- O̅mura Satoshi Memorial Institute and Graduate School of Infection Control Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Hiroki Yamagishi
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Richmond Sarpong
- Department of Chemistry, University of California, Berkeley, California 94720, United States
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4
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Vargas-Rivera MA, Liu AS, Ellman JA. Visible-Light-Mediated, Diastereoselective Epimerization of Exocyclic Amines. Org Lett 2023; 25:9197-9201. [PMID: 38114418 PMCID: PMC10771010 DOI: 10.1021/acs.orglett.3c03801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Stereoselective α-amino C-H epimerization of exocyclic amines is achieved via photoredox catalyzed, thiyl-radical mediated, reversible hydrogen atom transfer to provide thermodynamically controlled anti/syn isomer ratios. The method is applicable to different substituents and substitution patterns about aminocyclopentanes, aminocyclohexanes, and a N-Boc-3-aminopiperidine. The method also provided efficient epimerization for primary, alkyl and (hetero)aryl secondary, and tertiary exocyclic amines. Demonstration of reversible epimerization, deuterium labeling, and luminescence quenching provides insight into the reaction mechanism.
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Affiliation(s)
| | - Aidan S. Liu
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Jonathan A. Ellman
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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5
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Qiu G, Ni CL, Knowles RR. Isotopic Fractionation as a Mechanistic Probe in Light-Driven C-H Bond Exchange Reactions. J Am Chem Soc 2023; 145:11537-11543. [PMID: 37192535 PMCID: PMC10510749 DOI: 10.1021/jacs.2c11212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Here, we report a diagnostic framework for elucidating the mechanisms of photoredox-based hydrogen isotope exchange (HIE) reactions based on hydrogen/deuterium (H/D) fractionation. Traditional thermal HIE methods generally proceed by reversible bond cleavage and bond reformation steps that share a common transition state. However, bond cleavage and bond reformation in light-driven HIE reactions can proceed via multiple, non-degenerate sets of elementary steps, complicating both mechanistic analysis and attendant optimization efforts. Building on classical treatments of equilibrium isotope effects, the fractionation method presented here extracts information regarding the nature of the key bond-forming and bond-breaking steps by comparing the extent of deuterium incorporation into an exchangeable C-H bond in the substrate relative to the H/D isotopic ratio of a solvent reservoir. We show that the extent of fractionation is sensitive to the mechanism of the exchange process and provides a means to distinguish between degenerate and non-degenerate mechanisms for isotopic exchange. In model systems, the mechanisms implied by the fractionation method align with those predicted by thermochemical considerations. We then employed the method to study HIE reactions whose mechanisms are ambiguous on thermodynamic grounds.
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Affiliation(s)
| | | | - Robert R. Knowles
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
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6
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Cassels WR, Crawford ET, Johnson JS. Enantio- and Diastereoselective Mannich Reactions of ß-Dicarbonyls by Second Stage Diastereoconvergent Crystallization. ACS Catal 2023; 13:6518-6524. [PMID: 38046476 PMCID: PMC10688612 DOI: 10.1021/acscatal.3c01515] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
The synthesis of chiral α-monosubstituted-ß-dicarbonyls is a challenging task in asymmetric catalysis due to the rapid, typically uncontrolled, product racemization or epimerization under most reaction conditions. For this reason, diastereoselective additions of unsubstituted ß-dicarbonyls to π-electrophiles are unusual. Herein, we disclose a simple catalytic crystallization-driven enantio- and diastereoselective Mannich reaction for the synthesis of stereodefined α-monosubstituted-ß-keto esters, dissymmetric ß-diesters, dissymmetric ß-diketones, and ß-keto amides that productively leverages product epimerization in solution. Mechanistic studies suggest a scenario where the initial enantioselective, diastereodivergent skeletal assembly is catalyzed by a chiral tertiary amine organocatalyst, which then facilitates second stage crystallization-induced diastereoconvergence to provide the challenging α-stereocenter in excellent stereoselectivity.
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Affiliation(s)
- William R Cassels
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Evan T Crawford
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Jeffrey S Johnson
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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7
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Kang G, Park S, Han S. Synthesis of High-Order and High-Oxidation State Securinega Alkaloids. Acc Chem Res 2023; 56:140-156. [PMID: 36594722 DOI: 10.1021/acs.accounts.2c00719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Securinega alkaloids, composed of more than 100 members characterized by the compact tetracyclic scaffold, have fascinated the synthetic community with their structural diversity and notable bioactivities. On the basis of the structural phenotype, oligomerizations and oxidations are major biosynthetic diversification modes of the basic Securinega framework. Despite the rich history of synthesis of basic monomeric Securinega alkaloids, the synthesis of oligomeric Securinega alkaloids, as well as oxidized derivatives, has remained relatively unexplored because of their extra structural complexity. In the first half of this Account, our synthetic studies toward high-order Securinega alkaloids are described. We aimed to establish a reliable synthetic method to form C14-C15' and C12-C15' bonds, which are prevalent connection modes between monomers. During our total synthesis of flueggenine C (9), we have invented an accelerated Rauhut-Currier reaction capable of forming the C14-C15' bond stereoselectively. Installation of the nucleophilic functionality to the Michael acceptor, which ushers the C-C bond forming conjugate addition to follow the intramolecular pathway, was the key to success. The C12-C15' linkage, which was inaccessible via an accelerated Rauhut-Currier reaction, was established by devising a complementary cross-coupling/conjugate reduction-based dimerization strategy that enabled the total synthesis of flueggenines D (11) and I (14). In this approach, the C12-C15' linkage was established via a Stille cross-coupling, and the stereochemistry of the C15' position was controlled during the following conjugate reduction step. In the later half of this Account, our achievements in the field of high-oxidation state Securinega alkaloids synthesis are depicted. We have developed oxidative transformations at the N1 and C2-C4 positions, where the biosynthetic oxidation event occurs most frequently. The discovery of a VO(acac)2-mediated regioselective Polonovski reaction allowed us to access the key 2,3-dehydroallosecurinine (112). Divergent synthesis of secu'amamine A (62) and fluvirosaones A (60) and B (61) was accomplished by exploiting the versatile reactivities of the C2/C3 enamine moiety in 112. We have also employed a fragment-coupling strategy between menisdaurilide and piperidine units, which allowed the installation of various oxygen-containing functionality on the piperidine ring. Combined with the late-stage, light-mediated epimerization and well-orchestrated oxidative modifications, collective total synthesis of seven C4-oxygenated securinine-type natural products was achieved. Lastly, the synthesis of flueggeacosine B (70) via two synthetic routes from allosecurinine (103) was illustrated. The first-generation synthesis (seven overall steps) employing Pd-catalyzed cross-coupling between stannane and thioester to form the key C3-C15' bond enabled the structural revision of the natural product. In the second-generation synthesis, we have invented visible-light-mediated, Cu-catalyzed cross-dehydrogenative coupling (CDC) between an aldehyde and electron-deficient olefin, which streamlined the synthetic pathway into four overall steps. Organisms frequently utilize dimerization (oligomerization) and oxidations during the biosynthesis as a means to expand the chemical space of their secondary metabolites. Therefore, methods and strategies for dimerizations and oxidations that we have developed using the Securinega alkaloids as a platform would be broadly applicable to other alkaloids. It is our sincere hope that lessons we have learned during our synthetic journey would benefit other chemists working on organic synthesis.
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Affiliation(s)
- Gyumin Kang
- Department of Chemistry, Korea Advanced Institute of Science & Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Sangbin Park
- Department of Chemistry, Korea Advanced Institute of Science & Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Sunkyu Han
- Department of Chemistry, Korea Advanced Institute of Science & Technology (KAIST), Daejeon 34141, Republic of Korea
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8
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Shen Z, Vargas-Rivera MA, Rigby EL, Chen S, Ellman JA. Visible Light-Mediated, Diastereoselective Epimerization of Morpholines and Piperazines to More Stable Isomers. ACS Catal 2022; 12:12860-12868. [PMID: 36406894 PMCID: PMC9668057 DOI: 10.1021/acscatal.2c03672] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report a photocatalyzed epimerization of morpholines and piperazines that proceeds by reversible hydrogen atom transfer (HAT) and provides an efficient strategy for editing the stereochemical configurations of these saturated nitrogen heterocycles, which are prevalent in drugs. The more stable morpholine and piperazine isomers are obtained from the more synthetically accessible but less stable stereoisomers, and a broad scope is demonstrated in terms of substitution patterns and functional group compatibility. The observed distributions of diastereomers correlate well with the relative energies of the diastereomer pairs as determined by density functional theory (DFT) calculations. Mechanistic studies, including luminescence quenching, deuterium labeling reactions, and determination of reversibility support a thiyl radical mediated HAT pathway for the epimerization of morpholines. Investigation of piperazine epimerization established that the mechanism is more complex and led to the development of thiol free conditions for the highly stereoselective epimerization of N,N'-dialkyl piperazines for which a previously unrecognized radical chain HAT mechanism is proposed.
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Affiliation(s)
- Zican Shen
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | | | - Elizabeth L. Rigby
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074, United States
| | - Shuming Chen
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074, United States
| | - Jonathan A. Ellman
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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9
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Collective total synthesis of C4-oxygenated securinine-type alkaloids via stereocontrolled diversifications on the piperidine core. Nat Commun 2022; 13:5149. [PMID: 36056139 PMCID: PMC9440219 DOI: 10.1038/s41467-022-32902-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 08/23/2022] [Indexed: 11/08/2022] Open
Abstract
Securinega alkaloids have fascinated the synthetic chemical community for over six decades. Historically, major research foci in securinega alkaloid synthesis have been on the efficient construction of the fused tetracyclic framework that bears a butenolide moiety and tertiary amine-based heterocycles. These "basic" securinega alkaloids have evolved to undergo biosynthetic oxidative diversifications, especially on the piperidine core. However, a general synthetic solution to access these high-oxidation state securinega alkaloids is lacking. In this study, we have completed the total synthesis of various C4-oxygenated securinine-type alkaloids including securingines A, C, D, securitinine, secu'amamine D, phyllanthine, and 4-epi-phyllanthine. Our synthetic strategy features stereocontrolled oxidation, rearrangement, and epimerization at N1 and C2-C4 positions of the piperidine core within (neo)securinane scaffolds. Our discoveries provide a fundamental synthetic solution to all known securinine-type natural products with various oxidative and stereochemical variations around the central piperidine ring.
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10
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DeHovitz JS, Hyster TK. Photoinduced Dynamic Radical Processes for Isomerizations, Deracemizations, and Dynamic Kinetic Resolutions. ACS Catal 2022. [DOI: 10.1021/acscatal.2c02480] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Jacob S. DeHovitz
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Todd K. Hyster
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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11
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Kazerouni AM, Brandes DS, Davies CC, Cotter LF, Mayer JM, Chen S, Ellman JA. Visible Light-Mediated, Highly Diastereoselective Epimerization of Lactams from the Most Accessible to the More Stable Stereoisomer. ACS Catal 2022; 12:7798-7803. [DOI: 10.1021/acscatal.2c02232] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Amaan M. Kazerouni
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Daniel S. Brandes
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Cassondra C. Davies
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074, United States
| | - Laura F. Cotter
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - James M. Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Shuming Chen
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074, United States
| | - Jonathan A. Ellman
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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12
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Xiong MF, Ye BH. Regioselective Dehydrogenation of the Secondary Amine Complexes into Imine Complexes under Visible-Light Irradiation. Organometallics 2022. [DOI: 10.1021/acs.organomet.1c00683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ming-Feng Xiong
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou 510275, Guangdong, China
| | - Bao-Hui Ye
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou 510275, Guangdong, China
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13
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Davies SG, Fletcher AM, Roberts PM, Taylor CE, Thomson JE. Synthesis and Configuration of O-Acetyl Microgrewiapine A: Phantomization of O-Acetyl 6- epi-Microgrewiapine A. JOURNAL OF NATURAL PRODUCTS 2022; 85:306-312. [PMID: 34918520 DOI: 10.1021/acs.jnatprod.1c00847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The formation of O-acetyl microgrewiapine A is investigated. NMR data for the authentic sample derived from the natural product are corrected. Wholly synthetic samples, produced from reductive N-methylation of synthetic microcosamine A (to give synthetic microgrewiapine A) followed by O-acetylation, exhibit NMR data that are identical to those of the authentic sample. The previous report that this two-step transformation proceeds with epimerization at C-6 is thus shown to be in error: the purported sample of O-acetyl 6-epi-microgrewiapine A is structurally misassigned and is, in fact, O-acetyl microgrewiapine A. A plausible rationale for the structural misassignment is advanced.
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Affiliation(s)
- Stephen G Davies
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Ai M Fletcher
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Paul M Roberts
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Cameron E Taylor
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - James E Thomson
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
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Dutta S, Li B, Rickertsen DRL, Valles DA, Seidel D. C-H Bond Functionalization of Amines: A Graphical Overview of Diverse Methods. SYNOPEN 2021; 5:173-228. [PMID: 34825124 PMCID: PMC8612105 DOI: 10.1055/s-0040-1706051] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
This Graphical Review provides a concise overview of the manifold and mechanistically diverse methods that enable the functionalization of sp3 C-H bonds in amines and their derivatives.
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Affiliation(s)
- Subhradeep Dutta
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611, USA
| | - Bowen Li
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611, USA
| | - Dillon R L Rickertsen
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611, USA
| | - Daniel A Valles
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611, USA
| | - Daniel Seidel
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611, USA
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15
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Xiong MF, Peng HL, Zhang XP, Ye BH. Discrepancy between Proline and Homoproline in Chiral Recognition and Diastereomeric Photoreactivity with Iridium(III) Complexes. Inorg Chem 2021; 60:5423-5431. [PMID: 33818063 DOI: 10.1021/acs.inorgchem.1c00387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The chiral-recognition processes of homoproline (hpro) and [Ir(pq)2(MeCN)2](PF6) (pq is 2-phenylquinoline; MeCN is acetonitrile) are investigated, in favor of formation of the thermodynamically stable diastereomers Λ-[Ir(pq)2(d-hpro)] and Δ-[Ir(pq)2(l-hpro)]. Moreover, the diastereoselective photoreactions of Δ-[Ir(pq)2(d-hpro)] and Δ-[Ir(pq)2(l-hpro)] are reported in the presence of O2 at room temperature. Diastereomer Δ-[Ir(pq)2(l-hpro)] is dehydrogenatively oxidized into imino acid complex Δ-[Ir(pq)2(hpro-2H2)] (hpro-2H2 is 3,4,5,6-tetrahydropicalinate), while diastereomer Δ-[Ir(pq)2(d-hpro)] occurs by interligand C-N cross-coupling and dehydrogenative oxidation reactions, affording three products: Δ-[Ir(pq)(d-pqh)] [pqh is N-(2-phenylquinolin-8-yl)homoproline], Δ-[Ir(pq)2(hpro-2H2)], and Δ-[Ir(pq)2(d-hpro-2H6)] [hpro-2H6 is 2,3,4,5-tetrahydropicalinate]. The C-N cross-coupling and dehydrogenative oxidation reactions are competitive, and the dehydrogenative oxidation reactions are regioselective. By optimization of the photoreaction parameters such as the diastereomeric substrate, solvent, and temperature as well as base, each possible competitive product is selectively controlled. In addition, density functional theory calculations are performed to elucidate the distinctly chiral recognition between proline and hpro with an iridium(III) complex.
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Affiliation(s)
- Ming-Feng Xiong
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou 510275, Guangdong, China
| | - He-Long Peng
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou 510275, Guangdong, China
| | - Xue-Peng Zhang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education School of Chemistry and Chemical Engineering, Shananxi Normal University, Xi'an 710119, China
| | - Bao-Hui Ye
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou 510275, Guangdong, China
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